Yes definately. I was getting quite annoyed with trying to keep in melee range of feng lfr so i popped stampedind roar. I did not feel a lot faster... So I wondered what was going on.
Checking my speed multiple times later it seems like stampeding roar stacking has been reduced. BUT only in raids? o.O Dont quote me on this but I was running with 200% speed outside with stampeding roar and 166% inside a raid. Stealth is even worse... 98% speed?

Now couple that with Wild Charge not working on 80% of all raid mobs in MoP it seems we lost a lot of our mobility?!
I dont think I saw much difference in dash stacking. If someone else would like to test it i would be grateful